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Address Space Identifier - ASID

For ARMv7 -A/R systems, the MMU uses an ASID to distinguish between memory pages which have the same virtual address, but which are used by an individual task ( I.e. A task which uses non-Global memory). The ASID is an eight-bit value, from 0-255, assigned by the Operating System.


So, does that mean, for a normal, e.g. Linux system, there can be no more than 256 non-Global tasks running at one time? Should we assume that a piece of multi-threaded code would have a unique Task/Process Identifier (for scheduling purposes), for each thread, but all its threads would have the same ASID?


And what happens in a Type1 virtual system, with a Hypervisor and say, two Guest OS's? Presumably, each Guest kernel has its own ASID? And which OS is assigning the ASID to user tasks?

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